Transcript Review For Final - Eastern Illinois University

Review For Final
© Abdou Illia, Spring 2009
Network Architecture
Models
3
Data transport
Application
OSI Reference Model

7 layers

Each layer communicate
with its peer layer, and with
layer above and below it.

Different protocols at each
layer

Upper layer deal with
application issues, and are
implemented in software

Lower layers handle data
transport issues, and are
implemented in software and
hardware
Summary Questions
1.
(a) Name the 7 layers of the OSI model, (b)
Name OSI layers that deal with application
issues ? (b) Name the OSI layer that deal
with data transport issue ?
Answer: See previous slide
2)
Application programs used at the
application layer of the OSI Model include
word processing. T / F
3)
Upper layers of the OSI Model are usually
implemented in hardware devices. T / F
4
Internetworking
Summary Questions
1. The local area network shown in Figure 8-18 (p. 261) has
two hubs (X and Y) interconnecting the workstations and
servers. What workstations and servers will receive a copy of
a packet if the following workstations/servers transmit a
message:
Workstation 1 sends a message to workstation 3:
Workstation 2 sends a message to Server 1:
Server 1 sends a message to workstation 3:
2. Replace hub Y with a switch. Now, what workstations and
servers will receive a copy of a packet if the following
workstations/servers transmit a message:
Workstation 1 sends a message to workstation 3:
Workstation 2 sends a message to Server 1:
Server 1 sends a message to workstation 3:
6
Summary Questions
3. Do Internetworking Exercise 2
The exercise is available in the Notes section.
Check the link next to the Internetworking
II ppt notes (posted on Thu 2/5)
7
Fundamentals of Data &
Signals
Summary Questions
1.
Distinguish between digital and analog signals
Answer: (see class notes for details if needed):


Analog: Continuous waveform, State of signal (voltage
level, etc.) varies continuously among an infinite
number of states
Digital: Discrete (non-continuous) waveform, State of
signal remain constant during each clock-cycle, Few
possible states
2. Distinguish between digital and binary transmission
Answer: Digital: Few possible states (2-64 states)
Binary: 2 states
9
Attenuation
10

A signal starts at a transmitter with 10 watts of power and
arrived at a receiver with 5 watts of power. Calculate the loss
of power in dB.
1.
dB = 10 log10 (P2 / P1)
2.
dB = 10 log10 (5/10)
3.
dB = 10 log10 (0.5)
4.
dB = 10 (-0.3)
5.
dB = -3
Q: What is the decibel loss of a signal that starts at 50 watts and experiences a 10-watt loss over a given section of cable ?
Q: What is the decibel loss of a signal that loses half its power during the course of transmission ?
Frequency, Bandwidth
11
(See Fundamentals of Data & Signals – Continued ppt notes for details if needed)
Q: What is the frequency (in Hz) of a signal that repeats
80000 times within one minute ?
Answer: 80000 / 60 = 1333.33 Hz
Q: What is the bandwidth of a signal composed of frequencies
from 50 Hz to 500 Hz ?
Answer: |500 Hz – 50 Hz | = 450 Hz
Conducted and Wireless
Media
Summary Questions

13
What does cross talk interference mean ? How can crosstalk interference be reduced ?
If transmission wires are placed side by side, electromagnetic radiation is emitted by one
wire and picked up by the other. Twisting pair of wire reduce crosstalk interference.

What categories of twisted pair are usually used in LANs ?
Categories 3, 4, 5, 6, 7, 8

What are the advantages and disadvantages of STP compared to UTP ?
Advantage: better level of isolation from interference. Disadvantage: cost

What is the main difference between Baseband coaxial cable and Broadband coaxial cable ?
Baseband transmit signals in a single channel, whereas broadband uses multiple channels.

What are the advantages of Optical fiber compared twisted pair and coaxial cable ?
Speed, No significant noise, No interference, Long distance

Can you transmit video signal over twisted pair wire ? Explain
Yes, you can (e.g. Digital Video Service or DVS). Noise used to be a limiting factor.
School of Business
Eastern Illinois University
Local Area Networks
LAN Management
15
Summary Questions

What are the four factors to take into account in deciding how many
servers to use to implement a LAN’s services?
Answer: Optimization, reliability, security, cost

To what two devices does a print server usually connect?
Answer: To a printer via a parallel or USB cable, and to a hub/switch via UTP
or other transmission media.

In print service with a print server device, where does a print job go when it
leaves the client PC (not counting the hub or switch)?
Answer: The print job first goes to the computer where the print queue
manager program is installed, which puts it in a print queue.

Do you have to use special printers for print service?
Answer: You do not need special printers, because all printers come with a
parallel and/or USB port that could be used.
Servers

Single server Versus Multiple specialized Servers
–

Decision based on Cost, Optimization, Reliability, and Security
Optimization:
–
–
File servers need storage capacity and rapid access
Client/Server applications need very fast processors
16
Servers

17
Print Server: basically NIC + a parallel or USB port +
Random Access Memory + Intelligence to receive data and
commands from print queue manager program.
This is not a network
printer. Network printers
have built-in NICs & print
server hardware

Note: Possible to connect printer directly to file server, but
people might have to walk far to get their printout.
Summary Questions
18
Answers are in Week8SummaryQuestionsS09.doc (Review
section of course Website - Check Review Exam 2 link)
Your organization has 12 employees, each with his
or her own stand-alone PC running Windows 98.
Each computer has a 10 Mbps NIC that could work
with coaxial cable or twisted pair.
a) List all the additional hardware and software you
would have to buy to install a 100BaseTX LAN. Be
very sure that you list all the things the organization
will have to buy. The organization wishes to use
electronic mail, word processing, file sharing, and
print sharing with four existing printers fed with
parallel ports.
b) How many ports should the hub or switch have?
Explain.
Ethernet standards
19
Summary Questions
1.
20
Directory Applications has Subdirectories Databases
and WordProcessings. The Network administrator
assigns user Lee to the group Outer. The
administrator assigns Outer the access rights R, S,
and T in Directory Applications. (Don’t worry about
the meaning of R, S, and T. They are simply types
of rights.) The administrator assigns Outer the
access rights S, U, and V in Subdirectory Databases.
a) What access rights does user Lee have in
Directory Applications? Explain. b) What access
rights does user Lee have in Directory Databases?
Explain. c) What access rights does user Lee have in
Directory WordProcessings? Explain.
Applications
Databases
WordProcessings
Automatic Inheritance of Access Rights



21
Assigning rights to users or group in a directory
Rights automatically inherited in lower directories
Simplifies rights assignment
Assigned Browse
And Read Rights
Application
Word Processing
Inherits Browse
And Read Rights
Inherits Browse
And Read Rights
Database
Oracle
QuickDB
Automatic Inheritance of Access Rights

22
Blocking of Inheritance
–
–
If rights explicitly assigned in subdirectory, inheritance is blocked
Only assigned rights are effective
Assigned Browse
And Read Rights
Application
Word Processing
Assigned Browse
And Execute Rights
Inherit Browse
And Read Rights
Database
Oracle
QuickDB
(Browse and Execute Only)
School of Business
Eastern Illinois University
The Internet
24
The Internet
Browser
Network
Packet
Webserver
Software
Packet
Route
Router
User PC (Host)
Operating System
TCP/IP
IP Address =128.150.50.9
Webserver (Host)
Operating System
TCP/IP
IP Address=139.67.14.54
Host name =eiu.edu
IP address

25
32-bits and Dotted Decimal Notation
–
IP addresses are really strings of 32 bits (1s and 0s)
 10000000101010100001000100001101
–
To convert this to dotted decimal notation, first, divide
them into four bytes (also called octets)
 10000000 10101010 00010001 00001101
(Both octets and bytes are collections of eight bits)
–
Convert each binary (Base 2) octet into decimal (Base
10)
26
IP address
Position Place Value
Bit Decimal
(N)
(2N)
Binary
10100011
=
Decimal
163
Note: Starts with 0
7
6
5
4
3
2
1
0
128
64
32
16
8
4
2
1
1
0
1
0
0
0
1
1
128
0
32
0
0
0
2
1
163
27
IP Address structure

Each IP Address has two main parts:
Network Part
Local Part

Each Organization is given the Network Part by
an IP address Registrar (e.g: www.arin.net)

For Eastern Illinois University, this is 139.67
–
All IP Addresses for Eastern’s computers begin with
that Network Part
IP Address
139.67
American Registry for Internet Numbers
Check EIU’s IP registration info
IP Address structure

Network Parts is 8 to 24 bits long
–
–
For Eastern, it is 16 bits long
16 bits is only an example
Network Part
(8 to 24 bits)

Local Part
–

Total address is 32 bits, so if the network part is 8 bits, the
local part is 24 bits
Common way to refer to IP address structure:
–
–
x.x.x.x/# (where # is the number of bits in the network part)
e.g. 139.67.0.0/16
28
29
Network classes

The value of the bits in the first octet of an IP
address determines the Network class
Class
Leftmost
bits
Class A 0xxx
Class B 10xx
Class C 110x
1)
8 bits
16 bits
24 bits
For each of the following IP
addresses, give the class and the
network bits.
10101010111110000101010100000001
01010100111110000101010100000001
2)
Network Part
Length
Address range
What class does Eastern’s
network belong to? (Net. Part
=139.67)
0.x.x.x to 127.x.x.x
128.0.x.x to 191.255.x.x
192.0.0.x to 223.255.255.x
Position
(N)
7
6
5
4
3
2
1
0
Place Value
(2N)
128
64
32
16
8
4
2
1
Bit
Decimal
30
Host name

Host Names
–
eiu.edu
Like nicknames
 Not official addresses
 Each host must have an IP address
 But only some hosts have host names
 If you give it a host name, your browser must look
up IP address of host
Domain Name System (DNS)
31
DNS provides server’s IP addresses given their host names
Autoconfiguration

32
User PCs do not need permanent IP addresses
– They only need to be found within a use session
– They usually are given temporary IP addresses
to use on the Internet for a couple of days
– The duration of temporary address is usually a
few days. When the lease expired another
temporary address is a given.
Autoconfiguration service provides clients computers with
temporary IP addresses to use for communication with other
computers on the Internet.
Autoconfiguration

33
Request-Response Cycle
–
User software requests IP address for the user PC in
Autoconfiguration Request message
–
Autoconfiguration Response message contains temporary IP address
to use in current session
Autoconfiguration

Most popular autoconfiguration protocol is
DHCP
–
–
–

Dynamic Host Configuration Protocol
Built into Windows after Win 3.1
Supplies host with temporary IP address
DHCP can give more information too
–
–
–
Usually gives IP address of a default gateway
(Microsoft terminology for router)
Can give IP address of a local DNS host
Can give other information
34
Summary Questions
35
1.
a) Distinguish between IP address and host name. b) Which
is the official address of a host? c) Does a server host need an
IP address? d) Does your home PC need an IP address when
you are on the Internet? e) Does a server host need a host
name? f) Does your home PC need a host name when you are
on the Internet?
2.
Using the conversion system in slide #26, convert the
following IP address to dotted decimal notation: 10101010
11110000 11001100 01010101. (spaces are included to
facilitate reading.)
3.
Using the conversion system in slide #26, convert the
following dotted decimal IP address into a 32-bit IP address:
192.128.2.4
36
Summary Questions
4.
What are the two parts in IP addresses?
5.
a) Who assigns the Network part? b) The Local
part?
6.
a) When do we need DNS? b) What information do
you send in a DNS request message? c) What
information do you receive in a DNS response
message?
7.
a) What is autoconfiguration? b) What information
do we get back, at a minimum, in an
autoconfiguration response message? c) What other
information may we get back?